Product Ratings (No Rating)

Choose How Many Stars (5 Being the best)

Description

MY TAKE:You know the question; “What system would you choose if you were banished to a desert island, with no possibility of changing anything.” For me, that system would begin with Convergent Audio Technology electronics. C.A.T. has consistently made class-leading tube electronics that many feel have no peer in the industry, and I can’t argue with that. My experience has been that the C.A.T. gear sounds great - regardless of the system - and their amplifiers drive difficult loads like no other tube amps I’ve encountered.Mr. Stevens' products not only sound incredible, those interested in specifications will be blown away by the numbers. In the of the preamps, some of the lowest noise and distortion figures of any preamp - even solid state! Be sure and read some of the technical notes in the Stereophile review below. – Galen Carol

Convergent Audio Technology - Philosophy -

CAT’s philosophy is to design our products to neither add to, nor detract from, the music. We never attempt to cover up a design problem with another problem, nor do we try to introduce a supposedly complementary problem to “synergize” with it. Two wrongs do not make a right. Only the eradication of the problem is correct.

The SL1 Renaissance is the product of relentless refinement to the original SL1 introduced in 1985. We have identified and eliminated every electronic artifact. This preamplifier is designed to allow superior systems to reach their fullest potential.

Power Supply -

• External power supply chassis contains the transformer’s magnetic field eliminating it as a source of hum.

• Rectification, initial regulation, and noise filtering are all performed in the EPS thereby delivering pure quiet DC power into the main chassis eliminating the grain and dryness associated with noise intermodulation.

• Isolation transformer eliminates entry of radio frequency noise through the AC power line yielding greater benefits than any of the expensive add-on power line conditioners without any of their sonic shortcomings.

• Fastest tube preamplifier, without any of the high frequency circuit-induced edginess which slower preamps frequently substitute for real speed. This speed is maintained even into long runs of cable.

• Lowest open loop distortion of any preamp yields unforced detail and resolution as no other preamp can.

Stereophile - Black Path Edition: "It's only logical: The better an audio component, the less room for improvement. The CAT SL1 Renaissance was already an excellent preamp, so when Ken Stevens told me that an upgrade was available, I assumed that any sonic improvement would likely be modest.

I was wrong. Within a few minutes of listening to my SL1 Renaissance Black Path Edition, I knew I was hearing no minor improvement—an impression that solidified as the preamp continued to warm up and break in. My original plan had been to discuss the upgrade in a short sidebar to a review of a different product; having now heard the improvements, I felt they deserved a separate Follow-Up. Except as noted below, I played CDs through PS Audio's PerfectWave MemoryPlayer transport and PerfectWave DirectStream DAC. The speakers were Avantgarde Acoustic Uno Nanos, driven by a McIntosh MC275LE amplifier. All cables were Nordost Valhalla 2.

In my review of the PS Audio DirectStream DAC in the February 2015 issue, I compared driving the McIntosh MC275LE directly from the DirectStream's analog outputs vs through the CAT SL1 Renaissance, at matched levels. The DirectStream's operating system was the then-current v.1.2.1. My preference was for the signal played through the SL1 Renaissance—but, as I noted in the review, it was a close call: I had to switch back and forth at least a half-dozen times before I was confident in my conclusion.

I made the same comparison with the Black Path Edition (the DirectStream itself having been upgraded to the latest—and sonically superior—Yale OS). This time there was no contest: Through the Black Path, music was simply more open, with more clearly defined soundstages and a more dynamic presentation. Nor did I have to do much switching back and forth to arrive at this conclusion—the differences were immediately apparent.

I had already listened a couple of times to Eugene Istomin's recording of Mozart's Piano Concerto 21, with Gerard Schwarz conducting the Seattle Symphony Orchestra (CD, Reference RR-68CD), and while I thought its sound was excellent, the interpretation seemed a bit bland and lacking in energy. Listening to it through the Black Path Edition, I noticed a lot more in the way of subtle dynamic variation, with no lack of energy when that was called for, and with a most effective communication of the playful interplay between piano and orchestra. Admittedly, other variables were in play—my audio system had undergone some changes since the last time I'd listened to this recording—but when I bypassed the Black Path using the DirectStream's variable analog output, some of the subtle dynamic variations were obscured. The Black Path Edition had a special way with dynamics, revealing variations at both the subtle and extreme ends of the range.

A related factor, particularly evident in recordings of piano and of other percussion instruments, was the Black Path's rendering of intertransient silence. Percussive sounds generally seemed crisper—not sharper or exaggerated, but with less overhang of notes. Listening to Dick Hyman Plays Fats Waller (direct to CD, Reference RR-33DCD), I'd always been impressed with Hyman's technique; through the Black Path, his fingers seemed to fly even more effortlessly, or as if the action of his Bösendorfer 2905E reproducing piano had been tweaked for faster response. Quite remarkable.

Going through my audiophile checklist, all the important characteristics were improved: Soundstages were more clearly defined, with better focus on voices and instruments; tonal balances were as neutral as could be, with no warmth added or subtracted, or other departures from neutrality; trebles were extended but sweet; and bass was similarly extended and very natural in character. Noise, which can be a problem with tubed equipment, was simply absent in practical terms: With the volume control set to a normal listening level but without applying signal, I engaged and disengaged the Mute control and had to strain to hear any difference at all.

In my write-up of the SL1 Renaissance, I described it as having the much-desired combination of high transparency and high resolution. By transparency I mean a component's ability to get out of the way of the music, adding as little as possible of its own characteristic sound or coloration. By resolution I mean a component's ability to reveal the most minute recorded details. Although I didn't have a non-upgraded SL1 Renaissance on hand for an A/B comparison (and don't forget those other changes to my system), I'm comfortable in saying that the Black Path Edition further enhanced the SL1 Renaissance's transparency and resolution.

Ken Stevens is justifiably proud of the Black Path Edition's phono section ("Make sure you listen to some LPs," he told me). It was extremely quiet, and its switchable MC transformers and plug-in load resistors allow it to be optimized for use with a wide range of cartridges. In my 2009 review, I'd noted that the SL1 Renaissance's phono section was much quieter than that of the preceding model, the SL1 Ultimate. Not having the SL1 Renaissance and Black Path Edition available at the same time for a direct comparison, I'm reluctant to say that the latter sounded "much better," but it certainly sounded as good. My phono source consists of an aging Linn LP12 turntable with Ittok VII tonearm, and a similarly aging AudioQuest AQ7000nsx cartridge—a combination that, while very listenable, falls well short of the state of the art. I'm in the middle of upgrading to a new turntable, arm, and cartridge, but that will be a story for another day. My experience with the Black Path Edition told me that it will be easy to set it up to match my new cartridge, and that the SL1 will not be a limiting factor in optimizing the sound quality.

Conclusions: Convergent Audio Technology's SL1 Renaissance Black Path Edition is a preamplifier that can be described only with superlatives. It is simply a great preamp, and represents a major improvement on its predecessor, the SL1 Renaissance. But more than any of the specific component changes, such as the use of CAT's Black Path capacitor, the factor most responsible for the performance of the Black Path Edition is designer Ken Stevens's single-minded devotion to making his products the best they can be by selecting the best-sounding components and tweaking every aspect of the design for optimal sound quality.

Of course, a preamplifier is only one component of an audio system; at the risk of stating the self-evident, it can't, by itself, produce sound. Every component of an audio system is important, and the first link in the chain is the recording itself. But if everything else in the system is working right, the SL1 Renaissance Black Path Edition will get you closer to the music's soul." - Robert Deutsch.Full Review Here

Stereophile - SL-1 Renaissance (version prior to Black Path Edition): "It's quite an accomplishment, if you think about it. Is there any other audio product introduced nearly 25 years ago that, while keeping the same basic design, has continued to be developed, its designer's aim always being to provide the best possible sound rather than adding new features? I can't think of any. And while Convergent Audio Technology exhibits at the annual Consumer Electronics Show, it's been a long time since I've seen magazine ads for any CAT products. Ken Stevens seems to be following the "better mousetrap" theory of marketing—and, by all accounts, it has worked for him.

The latest SL1, the Renaissance, is a most worthy representative of this tradition. To use terms that have become hackneyed, its presentation is accurate as well as musical, allowing the system to reproduce music in a way that's faithful to the source and preserves musical values, with outstanding transparency, resolution, and dynamics. The SL1 Ultimate was an excellent preamp; in every musically relevant parameter, the SL1 Renaissance is comfortably ahead of it.

Is this the end of Ken Stevens' long development of the SL1? Has every aspect of the design and its execution been tweaked to the point at which no further improvement is possible? For now, the answer has to be "Yes." As for the future—well, knowing Ken Stevens, I wouldn't bet on it." - Robert Deutsch Full Review Here

Stereophile Measurements:"The SL1's RIAA correction (fig.1) was one of the most accurate I have measured, at less than ±0.05dB up to 10kHz. The MM input featured a slight rise above the audioband, the MC input a slightly early ultrasonic rolloff, reaching –3dB at 78kHz. Channel separation via the phono stage was good, at 61.5dB at middle and high frequencies, rising a little to 67.5dB at 20Hz. The unweighted, wideband noise floor of the phono stage was low via the MM input, at 67.6dB ref. 5mV at 1kHz, improving to 86dB when A-weighted. The MC input was less good, at 43dB ref. 500µV at 1kHz, due to the presence of some low-level 60Hz hum that I couldn't eliminate by experimenting with the grounding between the preamplifier and my test set. This improved to 58.3dB when A-weighted.

"The SL1 Renaissance's phono-stage overload margin was the best I have seen. The MM input offered 33dB of margin at low and middle frequencies before the measured THD+noise reached 1%, dropping to 22.5dB at 20kHz, which is still excellent. The corresponding figures for the MC input were 42.2 and 31.6dB. To put this in perspective, the MC input overloaded with a 1kHz tone at 64.33mV, more than 42dB higher than the nominal 500µV reference level, with an output voltage at the Tape output of 46.4V! The minimum THD+N figure was just 0.0094%, illustrated graphically in fig.2, the spectrum of the SL1's output with the MM input fed a 1kHz tone at 50mV. The highest-level harmonic is the second, at –99dB, and the only other harmonic visible above the noise floor is the third, at –110dB! The SL1's phono stage is basically overload-proof.

"Line-stage channel separation was superb at almost 100dB in both directions at 1kHz, but worse at higher frequencies due to the usual capacitive coupling between channels. It was still an excellent 70dB at 30kHz, however (fig.4). The wideband, unweighted signal/noise ratio (ref. 1V output with the input shorted but the volume control at its maximum) was 67.8dB in High Gain, 70.5dB in Low Gain. A-weighted, these figures improved to 91.3 and 96.4dB, respectively.

Choose How Many Stars (5 Being the best)

Description

MY TAKE:You know the question; “What system would you choose if you were banished to a desert island, with no possibility of changing anything.” For me, that system would begin with Convergent Audio Technology electronics. C.A.T. has consistently made class-leading tube electronics that many feel have no peer in the industry, and I can’t argue with that. My experience has been that the C.A.T. gear sounds great - regardless of the system - and their amplifiers drive difficult loads like no other tube amps I’ve encountered.Mr. Stevens' products not only sound incredible, those interested in specifications will be blown away by the numbers. In the of the preamps, some of the lowest noise and distortion figures of any preamp - even solid state! Be sure and read some of the technical notes in the Stereophile review below. – Galen Carol

Convergent Audio Technology - Philosophy -

CAT’s philosophy is to design our products to neither add to, nor detract from, the music. We never attempt to cover up a design problem with another problem, nor do we try to introduce a supposedly complementary problem to “synergize” with it. Two wrongs do not make a right. Only the eradication of the problem is correct.

The SL1 Renaissance is the product of relentless refinement to the original SL1 introduced in 1985. We have identified and eliminated every electronic artifact. This preamplifier is designed to allow superior systems to reach their fullest potential.

Power Supply -

• External power supply chassis contains the transformer’s magnetic field eliminating it as a source of hum.

• Rectification, initial regulation, and noise filtering are all performed in the EPS thereby delivering pure quiet DC power into the main chassis eliminating the grain and dryness associated with noise intermodulation.

• Isolation transformer eliminates entry of radio frequency noise through the AC power line yielding greater benefits than any of the expensive add-on power line conditioners without any of their sonic shortcomings.

• Fastest tube preamplifier, without any of the high frequency circuit-induced edginess which slower preamps frequently substitute for real speed. This speed is maintained even into long runs of cable.

• Lowest open loop distortion of any preamp yields unforced detail and resolution as no other preamp can.

Stereophile - Black Path Edition: "It's only logical: The better an audio component, the less room for improvement. The CAT SL1 Renaissance was already an excellent preamp, so when Ken Stevens told me that an upgrade was available, I assumed that any sonic improvement would likely be modest.

I was wrong. Within a few minutes of listening to my SL1 Renaissance Black Path Edition, I knew I was hearing no minor improvement—an impression that solidified as the preamp continued to warm up and break in. My original plan had been to discuss the upgrade in a short sidebar to a review of a different product; having now heard the improvements, I felt they deserved a separate Follow-Up. Except as noted below, I played CDs through PS Audio's PerfectWave MemoryPlayer transport and PerfectWave DirectStream DAC. The speakers were Avantgarde Acoustic Uno Nanos, driven by a McIntosh MC275LE amplifier. All cables were Nordost Valhalla 2.

In my review of the PS Audio DirectStream DAC in the February 2015 issue, I compared driving the McIntosh MC275LE directly from the DirectStream's analog outputs vs through the CAT SL1 Renaissance, at matched levels. The DirectStream's operating system was the then-current v.1.2.1. My preference was for the signal played through the SL1 Renaissance—but, as I noted in the review, it was a close call: I had to switch back and forth at least a half-dozen times before I was confident in my conclusion.

I made the same comparison with the Black Path Edition (the DirectStream itself having been upgraded to the latest—and sonically superior—Yale OS). This time there was no contest: Through the Black Path, music was simply more open, with more clearly defined soundstages and a more dynamic presentation. Nor did I have to do much switching back and forth to arrive at this conclusion—the differences were immediately apparent.

I had already listened a couple of times to Eugene Istomin's recording of Mozart's Piano Concerto 21, with Gerard Schwarz conducting the Seattle Symphony Orchestra (CD, Reference RR-68CD), and while I thought its sound was excellent, the interpretation seemed a bit bland and lacking in energy. Listening to it through the Black Path Edition, I noticed a lot more in the way of subtle dynamic variation, with no lack of energy when that was called for, and with a most effective communication of the playful interplay between piano and orchestra. Admittedly, other variables were in play—my audio system had undergone some changes since the last time I'd listened to this recording—but when I bypassed the Black Path using the DirectStream's variable analog output, some of the subtle dynamic variations were obscured. The Black Path Edition had a special way with dynamics, revealing variations at both the subtle and extreme ends of the range.

A related factor, particularly evident in recordings of piano and of other percussion instruments, was the Black Path's rendering of intertransient silence. Percussive sounds generally seemed crisper—not sharper or exaggerated, but with less overhang of notes. Listening to Dick Hyman Plays Fats Waller (direct to CD, Reference RR-33DCD), I'd always been impressed with Hyman's technique; through the Black Path, his fingers seemed to fly even more effortlessly, or as if the action of his Bösendorfer 2905E reproducing piano had been tweaked for faster response. Quite remarkable.

Going through my audiophile checklist, all the important characteristics were improved: Soundstages were more clearly defined, with better focus on voices and instruments; tonal balances were as neutral as could be, with no warmth added or subtracted, or other departures from neutrality; trebles were extended but sweet; and bass was similarly extended and very natural in character. Noise, which can be a problem with tubed equipment, was simply absent in practical terms: With the volume control set to a normal listening level but without applying signal, I engaged and disengaged the Mute control and had to strain to hear any difference at all.

In my write-up of the SL1 Renaissance, I described it as having the much-desired combination of high transparency and high resolution. By transparency I mean a component's ability to get out of the way of the music, adding as little as possible of its own characteristic sound or coloration. By resolution I mean a component's ability to reveal the most minute recorded details. Although I didn't have a non-upgraded SL1 Renaissance on hand for an A/B comparison (and don't forget those other changes to my system), I'm comfortable in saying that the Black Path Edition further enhanced the SL1 Renaissance's transparency and resolution.

Ken Stevens is justifiably proud of the Black Path Edition's phono section ("Make sure you listen to some LPs," he told me). It was extremely quiet, and its switchable MC transformers and plug-in load resistors allow it to be optimized for use with a wide range of cartridges. In my 2009 review, I'd noted that the SL1 Renaissance's phono section was much quieter than that of the preceding model, the SL1 Ultimate. Not having the SL1 Renaissance and Black Path Edition available at the same time for a direct comparison, I'm reluctant to say that the latter sounded "much better," but it certainly sounded as good. My phono source consists of an aging Linn LP12 turntable with Ittok VII tonearm, and a similarly aging AudioQuest AQ7000nsx cartridge—a combination that, while very listenable, falls well short of the state of the art. I'm in the middle of upgrading to a new turntable, arm, and cartridge, but that will be a story for another day. My experience with the Black Path Edition told me that it will be easy to set it up to match my new cartridge, and that the SL1 will not be a limiting factor in optimizing the sound quality.

Conclusions: Convergent Audio Technology's SL1 Renaissance Black Path Edition is a preamplifier that can be described only with superlatives. It is simply a great preamp, and represents a major improvement on its predecessor, the SL1 Renaissance. But more than any of the specific component changes, such as the use of CAT's Black Path capacitor, the factor most responsible for the performance of the Black Path Edition is designer Ken Stevens's single-minded devotion to making his products the best they can be by selecting the best-sounding components and tweaking every aspect of the design for optimal sound quality.

Of course, a preamplifier is only one component of an audio system; at the risk of stating the self-evident, it can't, by itself, produce sound. Every component of an audio system is important, and the first link in the chain is the recording itself. But if everything else in the system is working right, the SL1 Renaissance Black Path Edition will get you closer to the music's soul." - Robert Deutsch.Full Review Here

Stereophile - SL-1 Renaissance (version prior to Black Path Edition): "It's quite an accomplishment, if you think about it. Is there any other audio product introduced nearly 25 years ago that, while keeping the same basic design, has continued to be developed, its designer's aim always being to provide the best possible sound rather than adding new features? I can't think of any. And while Convergent Audio Technology exhibits at the annual Consumer Electronics Show, it's been a long time since I've seen magazine ads for any CAT products. Ken Stevens seems to be following the "better mousetrap" theory of marketing—and, by all accounts, it has worked for him.

The latest SL1, the Renaissance, is a most worthy representative of this tradition. To use terms that have become hackneyed, its presentation is accurate as well as musical, allowing the system to reproduce music in a way that's faithful to the source and preserves musical values, with outstanding transparency, resolution, and dynamics. The SL1 Ultimate was an excellent preamp; in every musically relevant parameter, the SL1 Renaissance is comfortably ahead of it.

Is this the end of Ken Stevens' long development of the SL1? Has every aspect of the design and its execution been tweaked to the point at which no further improvement is possible? For now, the answer has to be "Yes." As for the future—well, knowing Ken Stevens, I wouldn't bet on it." - Robert Deutsch Full Review Here

Stereophile Measurements:"The SL1's RIAA correction (fig.1) was one of the most accurate I have measured, at less than ±0.05dB up to 10kHz. The MM input featured a slight rise above the audioband, the MC input a slightly early ultrasonic rolloff, reaching –3dB at 78kHz. Channel separation via the phono stage was good, at 61.5dB at middle and high frequencies, rising a little to 67.5dB at 20Hz. The unweighted, wideband noise floor of the phono stage was low via the MM input, at 67.6dB ref. 5mV at 1kHz, improving to 86dB when A-weighted. The MC input was less good, at 43dB ref. 500µV at 1kHz, due to the presence of some low-level 60Hz hum that I couldn't eliminate by experimenting with the grounding between the preamplifier and my test set. This improved to 58.3dB when A-weighted.

"The SL1 Renaissance's phono-stage overload margin was the best I have seen. The MM input offered 33dB of margin at low and middle frequencies before the measured THD+noise reached 1%, dropping to 22.5dB at 20kHz, which is still excellent. The corresponding figures for the MC input were 42.2 and 31.6dB. To put this in perspective, the MC input overloaded with a 1kHz tone at 64.33mV, more than 42dB higher than the nominal 500µV reference level, with an output voltage at the Tape output of 46.4V! The minimum THD+N figure was just 0.0094%, illustrated graphically in fig.2, the spectrum of the SL1's output with the MM input fed a 1kHz tone at 50mV. The highest-level harmonic is the second, at –99dB, and the only other harmonic visible above the noise floor is the third, at –110dB! The SL1's phono stage is basically overload-proof.

"Line-stage channel separation was superb at almost 100dB in both directions at 1kHz, but worse at higher frequencies due to the usual capacitive coupling between channels. It was still an excellent 70dB at 30kHz, however (fig.4). The wideband, unweighted signal/noise ratio (ref. 1V output with the input shorted but the volume control at its maximum) was 67.8dB in High Gain, 70.5dB in Low Gain. A-weighted, these figures improved to 91.3 and 96.4dB, respectively.